Tuesday, September 27, 2005
Monday, September 26, 2005
Sunday, September 25, 2005
Tuesday, September 20, 2005
The tactic helps bind families without the dangers of inbreeding
This serves to bind families together, but avoids the dangers of inbreeding.
The females live together in groups segregated from the opposite sex, but gang together to prowl for males once the mating season arrives.
Scientists from the University of Bristol and Queen Mary in London made the discovery using genetic techniques to construct family trees for the bats.
Most female greater horseshoe bats (Rhinolophus ferrumequinum) seek out the same male to mate with year after year.
The bats produce only one offspring each year, so each animal represents the outcome of a separate mating.
Stephen Rossiter, of Queen Mary, University of London, and colleagues used genetic typing to compile the family trees of some 452 bats at Woodchester Mansion in Gloucestershire, UK.
The researchers mapped male partners on to pedigrees of female bats to examine patterns of pairings down the years.
They found that relatives on the maternal line shared male partners more often than would be expected by chance.
In all, they detected 20 groups of related females sharing mates, with two to five individuals in each of these groups.
Dr Rossiter believes that by sharing sexual partners, the greater horseshoe bat "strengthens social ties and promotes greater levels of cooperation within the colony".
It pays to share
Kinship between individual animals is extremely important for cooperation and, therefore, social cohesion, says Dr Rossiter and his team.
The tendency for females to return to the same males each year also strengthens this kinship.
Any behaviour, such as this, which increases the levels of relatedness within social groups while dodging the costs of inbreeding is likely to be favoured by natural selection, the researchers write.
In the UK, greater horseshoe bats are thought to have declined by 90% over the past 100 years.
This may be due to the disturbance of roosts and changing farming practices, since the use of pesticides has caused a declined in the insects they prey on.
Monday, September 19, 2005
Scientists in Israel have just developed a new technique to retrieve better quality, less contaminated DNA from very old remains, including human bones.
It could aid the study of the evolution and migration of early modern humans, as well as extinct populations such as our close relatives, the Neanderthals.
Many researchers would dearly love to get their hands on DNA samples from hominids further back in time - from those that lived 100,000 years ago or more - to find out how they were related to people alive today.
But fossil studies this far back in time have long been hindered by contamination with foreign genetic material and the problem of recovering long, intact DNA sequences.
The new method provides hope, however.
"DNA gets everywhere. So when we're dealing with a sample and you find it's got human DNA in it - is that DNA from the fossil, or is it actually DNA from the person who unearthed it?" says Professor Chris Stringer, the head of human origins at the Natural History Museum in London, UK.
"It breaks up into very small fragments so it is quite technically complicated to put it all back together again," explains Dr Robert Foley, the director of the Leverhulme Centre for Human Evolutionary Studies at the University of Cambridge, UK.
Freezing provides the ideal preservation conditions. The most widely accepted oldest DNA yet isolated comes from 400,000-year-old plants found in ice in Siberia. But most specimens are not excavated from such places.
An improved technique for retrieving DNA from fossil bone, just published in the journal Proceedings of the National Academy of Sciences (PNAS), may help.
Dr Michal Salamon, from the Weizmann Institute of Science in Rehovot, Israel, and colleagues, showed that "crystal aggregates", small mineral pockets formed during fossilisation, can preserve DNA better than the rest of the bone.
They compared DNA extracted from these crystal aggregates with genetic material taken from untreated, whole-bone powder. The samples were taken from eight different modern and fossil bones.
This approach, "significantly improves the chances of obtaining authentic ancient DNA sequences, especially from human bones", they told PNAS.
Commenting on the latest research, Dr Michael Hofreiter, from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who helped decode 40,000-year-old nuclear DNA from a cave bear earlier this year, said: "It's possible; but there need to be more studies on more samples, and they need to show that you don't get human contamination of animal bones.
"Then I would believe that it is a breakthrough for ancient DNA research."
The big split
Scientists are hopeful the new technique will help them get at the DNA in the chromosomes of a cell - the nuclear DNA.
Ancient DNA research has so far mainly focused on mitochondria, the tiny "power-stations" of the cell. These exist outside of the nucleus and have their own DNA. And, although this information is very useful, it is more limited in its scope than that which could be obtained from nuclear DNA.
"There's about 1,000 times more mitochondrial DNA than nuclear DNA in our cells, so it's much easier to pick up," explains Professor Stringer.
The mitochondrial DNA is inherited only through the egg - through females. This means it is a useful marker for tracing a line back into the past, as it has never been mixed with DNA from males.
"One of the most important discoveries from studying ancient mitochondrial DNA is the estimate of when humans diverged in evolution from the Neanderthals - around half a million years ago," according to Dr Foley.
Professor Stringer adds: "We've now got about 10 Neanderthal specimens of around 40-50,000 years old that have yielded DNA that is clearly distinct from anyone alive today."
This means scientists can be sure that it is ancient, not just modern DNA from contamination.
It has also given them a measure of how different Neanderthals were from modern people.
"Neanderthals are three times as different from us as we all are from each other," says Professor Stringer.
But there remains the hotly debated question of whether Neanderthals were a completely separate species to us. Professor Stringer says that they are if that assessment is based on studying their bone anatomy.
However, the evidence from mitochondrial DNA is somewhat ambiguous.
"The mitochondrial DNA on its own can't tell us if we're a distinct species," he explains.
"It depends what mammal you take. There are some species where the difference in mitochondrial DNA between us and Neanderthals would say they were a different species.
"Whereas in chimpanzees, our closest relative, you could contain the variation between us and Neanderthals in a single species alive today in Africa."
Scientists need to recover better DNA from our fossils, especially the nuclear DNA.
"Each gene has a separate evolution so to understand Neanderthals properly we will need different bits of their DNA to see if they're all telling us the same story," he adds.
The male sex chromosome (the "Y") is useful for tracking male inheritance, since males inherit their Y chromosome only from their father.
Using both mitochondrial and Y chromosome DNA from people alive today, complex pathways have been mapped for how modern humans got to where they are - but there are problems.
Dr Mim Bower, an ancient DNA researcher at the McDonald Institute for Archaeological Research in Cambridge, UK, gives an example.
"Using modern DNA we see a different pattern of settlement in the Pacific islands between men and women - the mitochondrial DNA patterns show a different migration pattern to the Y chromosome DNA."
Studying the DNA not of modern humans but of their distant ancestors could help answer such questions.
"At the moment we can't follow that into the past as it's very difficult to get nuclear DNA," Dr Bower says.
This is especially problematic for the Y chromosome, which is nuclear.
Source: The Genographic Project
Sunday, September 18, 2005
Costs – and NASA's reputation for going over budget on large programmes – are major hurdles the agency will have to overcome to send people back to the Moon, say outside experts.
NASA administrator Michael Griffin unveiled the agency's scheme to return humans to the Moon on Monday. It involves building on existing space shuttle technology and proven methods of landing people on the Moon, drawn from the Apollo programme.
A reusable capsule will be fitted atop a longer shuttle rocket booster to send a four-person crew into space. Separately, a heavy-lift launcher will deliver other elements of the Moon-bound ship into orbit. All of this is supposed to be developed and tested before the project's first lunar landing in 2018.
Griffin says the mission could cost at least $104 billion. He says the agency would adopt a pay-as-you-go approach and would not need to drastically increase its budget, now at about $16 billion per year. But critics are unconvinced.
Currently, NASA's share of the federal budget is about 0.7%. During the Apollo era, NASA took up as much as 4% of the US budget.
NASA has been widely criticised for its accounting practices – especially in its human spaceflight programme. "Given the funding shortfalls in the space shuttle programme, there is simply no credible way to accelerate the development of a Crew Exploration Vehicle unless the NASA budget increases more than has been anticipated," says Congressman Sherwood Boehlert, chairman of the US House Science Committee.
"Whether such an increase is a good idea in the context of overall federal spending at this time is something neither Congress nor the Administration has yet determined," he adds.
It’s rocket science
"I don't think this plan will succeed," says Alex Roland, a history professor at Duke University in Durham, North Carolina, US. "It's plausible in a certain way because they have taken things from Apollo and the shuttle that were reasonably successful and good. Who knows whether or not you can quickly and cheaply cobble those together into a workable system?"
But others defend the plan, arguing the agency needs to move beyond its current Earth-orbiting shuttle and space station programmes. "It's obvious there's a rocket scientist running NASA again," says Elliot Pulham, president and chief executive officer of the Space Foundation, a non-profit space advocacy group. "I wish I was still young enough to go."
But even the spirit of exploration is not enough to convince everyone to spend billions on the project. As Roland put it: "I think this whole enterprise of trying to put people on the Moon and then put people on Mars begs the question: what for?"
Saturday, September 17, 2005
|Image: COURTESY OF THE PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES|
The increased amount of dissolved solids in the water is strongly correlated to the amount of impervious surfaces such as roads and parking lots. In some regions, the increased use of deicer compounds in the winter caused chloride levels to reach five grams per liter, approximately a quarter of that found in seawater. Because land-use changes so rapidly, the authors conclude that "salinization associated with increasing suburban and urbanization deserves attention as one of the most significant threats to the integrity of freshwater ecosystems in the northeastern U.S."
Sadly, and despite claims of substantial progress from politicians and their spin doctors, the summit has failed.
There was no agreement on disarmament, no reform of the Security Council and no commitment to aid targets that might help alleviate poverty.
Even the Security Council's condemnation of terrorism was undermined by a failure to agree what "terrorism" actually means.
The disappointment was clearly expressed by the UN's Secretary-General Kofi Annan. "We have not yet achieved the sweeping and fundamental reform that I and many others believe is required," he told delegates.
One area that will inevitably suffer as a result are efforts to improve access to the internet, yet the global digital divide is becoming a major development issue precisely because of the net's success in the developed world.
Education, trading and social contacts increasingly depend on it, and being cut off from the network is now just as damaging to a local economy as trade barriers or tariffs.
Later, recognising the importance of information and communication technologies in achieving these goals, the World Summit on the Information Society (WSIS) was convened to consider how to build the framework of an "all-inclusive and equitable" information society.
The first WSIS meeting took place in Geneva in 2003, and it meets again in Tunis later this year. But without a clear mandate from the UN the discussions seem doomed to be ineffectual, filled with well-meaning platitudes but unable to deliver either resources or political change.
Since the politicians are failing us, we need to look elsewhere for breakthroughs that can change people's lives by making it possible for them to get online so that we can let the next five billion users join those of us who already have a connection to the net.
Part of the problem is how we ensure the network reaches everyone, but the problems do not stop there.
Throughout the world there are people working on a whole range of technologies, from fuel cells that can provide a reliable power source for rural networks to the much-publicised $100 computer project led by Nicholas Negroponte at MIT, and all of this work is important.
One of the research bodies funding academic work in the UK, the EPSRC, has offered £1m from its "Ideas Factory" budget to pay for "novel and adventurous approaches" to the challenge of bridging the global digital divide.
Instead of just asking academics to send in bids for some or all of the pot, they are holding a five-day meeting near Bath later in the year, inviting researchers from the widest possible range of disciplines to work together and come up with new ideas and new ways of tackling the problem.
It is called a "sandpit", and according to Cambridge University computer scientist Alan Blackwell, who will be leading the discussion, it is a great way to encourage creativity and generate unexpected approaches and project proposals.
And after five days there should be a fundable research project that can make a difference to the digitally dispossessed.
Initiatives like this are absolutely vital, and I cannot wait to see what they come up with. But we cannot afford to give up on the political process entirely.
Whatever great ideas we have for low-cost computers or new energy supplies, bridging the global digital divide requires us to bridge another divide first - the one between the world's senior politicians and the people who can come up with creative and affordable solutions to practical problems.
We must not forget that high-level action is capable of delivering resources at a level that university researchers, voluntary organisations or even businesses can only dream of - $50bn of aid for the area affected by Hurricane Katrina shows what can be done once the political will is there.
Without the technologies and the practical solutions to the problems on the ground, the politicians will have nothing to fund.
While five days of debate, discussion and, inevitably, disagreement in Bath for £1m of funding may not seem like it is going to change the world, we may be surprised by what emerges when a bunch of clever people are given a chance to think out loud.And then we can try to make the politicians listen to what they say.
The detailed map shows areas likely to be methane frost and a bright spot perhaps made of frozen carbon monoxide.
And another team has obtained the most precise estimate yet for the size of its moon, Charon, with data gathered during the planet's eclipse of a star.
This figure could be used to calculate a more accurate size for Pluto itself.
The US space agency's (Nasa) New Horizons spacecraft will set off for an encounter with Pluto and Charon next year, but will not arrive until 2015 at the earliest.
Until then, astronomers say they will continue to seek insights into this mysterious world and its lone satellite.
The latest global map was produced using data obtained by Hubble's Advanced Camera for Surveys (ACS) between July 2002 and June 2003.
The telescope worked over 12 orbits and looked through two filters. Producing the map has taken two years of computer processing.
The researchers, led by Marc Buie of the Lowell Observatory, have found dark areas thought to be dirty water-ice and brighter ones indicating nitrogen frost. Red areas indicate methane ice and possibly other organics (carbon-based molecules).
The methane frost seems to be everywhere, running into dark and light areas on "a hemispheric level", said Dr Buie.
An unusual bright spot near the centre of the global map could indicate the presence of carbon monoxide, said Dr Buie. The Lowell Observatory researcher said he had asked members of the New Horizons team to investigate this area with their spacecraft.
Bruno Sicardy, from the Paris Observatory, France, and colleagues used the data from this event to tie down the radius of Charon to 602.5km, plus or minus one kilometre - the most precise figure yet obtained for its size.
Previous observations had given a lower limit for Charon's size, but could not say how big it might be.
From the new radius, Dr Sicardy's team was able to determine a very accurate density for Charon of 1.73 (plus or minus 0.08) grams per cubic centimetre.
Planet under question
Astronomers can now re-analyse data on Pluto gathered in the 1980s using the new figures for Charon's size and density to better constrain these values for Pluto itself.
Recent discoveries in the outer Solar System have cast doubt on Pluto's status as a planet. Some think it is simply the first historically recorded representative of a larger family of distant bodies known as Kuiper belt objects.
Dr Buie explained that Pluto seemed to be very similar to Neptune's moon Triton, which is thought to be a Kuiper belt object captured by Neptune's gravity. This is despite the fact that the process of capture should have altered Triton's surface drastically through heating.
"I'm surprised Triton and Pluto aren't more different than they are," he told the BBC News website.
The primary launch window for the New Horizons mission runs from 11 January-14 February 2006. If it launches within that window, it will swing by Jupiter for a gravity assist and arrive at Pluto in 2015.
Friday, September 16, 2005
Hawking has still to provide a fully worked mathematical proof
His popular science book A Brief History of Time was a publishing sensation, staying at the top of the best-seller lists longer than any other book in recent history.
But behind the public face lies an argument that has been raging for almost 30 years.
Hawking shot to fame in the world of physics when he provided a mathematical proof for the "Big Bang" theory.
This theory showed that the entire Universe exploded from a singularity - an infinitely small point with infinite density and infinite gravity. Hawking was able to come to his proof using mathematical techniques that had been developed by Roger Penrose.
However, Penrose's techniques were developed to deal not with the beginning of the Universe but with black holes.
Science had long predicted that if a sufficiently large star collapsed at the end of its life, all the matter left in the star would be crushed into an infinitely small point with infinite gravity and infinite density - a singularity.
Hawking realised that the Universe was, in effect, a black hole in reverse; instead of matter being crushed into a singularity, the Universe began when a singularity expanded to form everything we see around us today - from stars to planets to people.
Hawking realised that to come to a complete understanding of the Universe, he would have unravel the mysteries of the black hole.
Hawking and his fellow physicist embarked on an extraordinary intellectual expedition - to tame the black hole. The period from the early 70s to the early 80s became known as the "Golden Age" of black hole research.
Slowly physicists were coming to understand its nature.
But Hawking realised that there was something missing from the picture that was emerging. All work on black holes to that point used the physics of the large-scale Universe.
The physics of gravity - first developed by Newton and then refined by Einstein's theories of general and special relativity. Hawking realised that to come to a full understanding of black holes, physicists would also have to use the physics of the small-scale Universe; the physics that had been developed to explain the movements of atoms and sub-atomic particles known as quantum mechanics.
The only problem was that no one had ever combined these two areas of physics before. This didn't deter Hawking. He set about developing a new way to force the physics of quantum mechanics to co-exist with Einstein's relativity within the intense gravity of a black hole.
After months of work, Hawking came up with a remarkable result. His equations were showing him that something was coming out of the black hole.
This was supposed to be impossible - the one thing that everyone thought they knew about black holes was that things went in but nothing, not even light itself, could escape.
The more Hawking checked, the more he was convinced he was right. He could see radiation coming out of the black hole. And it led him to the realisation that this radiation (later called Hawking radiation) would cause the black hole to evaporate and eventually disappear.
Although Hawking's theories about black hole evaporation were revolutionary, they soon came to be widely accepted. But Hawking felt that this work had far more fundamental consequences.
In 1976 he published a paper in Physical Review D called, "The breakdown of predictability in gravitational collapse". In this paper, Hawking argued that it wasn't just the black hole that disappeared.
He said that all the information about everything that had ever been inside the black hole disappeared, too.
The reason physicists cling on to the idea that information can't be lost is that it's their link with either the past or the future. If information is lost then science can never know the past or predict the future. There are limits to what science can know.
For many years, no one took much notice of Hawking's ideas until a fateful meeting in San Francisco.
Hawking presented his ideas to some of the world's leading physicists, and in the audience were two particle physicists, Gerard t'Hooft and Leonard Susskind.
They were shocked. They both grasped that Hawking's "breakdown of predictability" applied not only to black holes but to all processes in physics.
The long search
According to Susskind, if Hawking's ideas were correct then it would infect all physics; there would no longer be any direct link between cause and effect. Physics would become impotent.
Since that meeting the "information paradox" has come to be seen as one of the most fundamental and most difficult problems in physics.
Arguments effectively boiled down into two camps. On the one side, Susskind and those who believed that Hawking was wrong and that information could not be lost - and on the other, Hawking and those who believed that physics would have to be re-written to take into account the uncertainty about information that Hawking had uncovered.
For 20 years, arguments raged. No side was willing to admit defeat... until a paper emerged written by a brilliant young Argentinean mathematician known as Juan Maldacena.
This paper claimed to be a rigorous mathematical explanation of what happened to information in black holes - and it showed that information was not lost. Hawking, it seemed, was on the losing side. But Hawking was not convinced.
Hawking set to work with a young research student, Christophe Galfard, to try to pick apart the Maldacena paper.
They thought they could use the same mathematical techniques employed by Maldacena to prove that information was in fact lost. But after two years' work, they still could not prove their thesis.
Then disaster struck, Stephen Hawking was taken ill with pneumonia and rushed to hospital; doctors feared for his life.
Hawking was kept in hospital for over three months. But whilst others fussed over his health, Hawking was thinking. Finally, on what many feared might be his death bed, he thought he'd come across what had eluded him for the past 30 years - a solution to the information paradox.
Once again, Hawking defied doctors' dire predictions and was soon at work, working on a new proof for the information paradox.
Then in July last year, at one of the most prestigious conferences in physics, Hawking made a dramatic announcement.
Hawking presented the outline of a proof that he hoped would at last solve the problem that he had posed almost 30 years earlier. However, despite the bold claims, some physicists remain unconvinced.
Over a year has passed since the conference and Hawking has still not presented a fully worked mathematical proof to back up his ideas.
But Hawking is a stubborn man. If he is going to change his mind on a belief he held for almost 30 years then it will be with his own proof, in his own time.
In spite of failing health and increasing problems communicating with his colleagues, Hawking is still working on the proof.
If he succeeds in completing a proof that convinces his colleagues, he will not only have solved one of the most difficult problems in physics but he will have produced ground-breaking work at the very end of his career.
That would be a feat that even his hero Einstein could not accomplish.
Thursday, September 15, 2005
|Image: COURTESY OF MARTIN H. TRAUTH|
Martin H. Trauth of the University of Potsdam in Germany and his colleagues found evidence for these wet periods in the sedimentary record of East Africa's Rift Valley lakes. The sediments contain assemblages of diatoms (silica algae), which are well known to be sensitive environmental indicators and can be used to reconstruct water depth and salinity. Studying the ancient diatoms, the team identified three times during which the lakes were deep as a result of regional climate change. These episodes also correlate with significant global climatic changes.
Rapid shifts between sustained periods of humidity and aridity, the researchers propose, would have provided the stress required for species to diverge. It is perhaps no coincidence, then, that the interval between three million and one million years ago witnessed the emergence of the genus Homo, the rise of Homo erectus and the first migration of hominids out of Africa, among other paleoanthropological events of note. A paper detailing these findings was published today in the journal Science.
The animals were sighted off the Mississippi coastline on Saturday after being washed away from the Marine Life Aquarium in Gulfport.
Rescuers plan to train them to jump on to mats alongside their boats and take them to salt-water tanks to recover.
The bottlenose dolphins have lived most of their lives in captivity and cannot fend for themselves in the wild.
Moby Solangi, owner of the Marine Life Aquarium, said there was huge concern for the wellbeing of the animals.
She said: "Once we realised the dolphins had been swept out to sea during the hurricane, we feared that they had died.
US National Oceanic and Atmospheric Administration
"We are just thrilled that they have stayed together during the past couple of weeks."
Experts from the US National Oceanic and Atmospheric Administration Fisheries Service are helping with the rescue attempt.
NOAA Fisheries spokeswoman Connie Barclay said if the animals cannot be trained, they will have to be captured in nets.
"They'll surely die if we don't rescue them," she said.
Rescuers are waiting for salt-water tanks to be shipped in by the US Navy.
A wave estimated to be 40ft (12m) high swept the mammals from their tank at the aquarium and into the Mississippi Sound when Katrina struck on 29 August.